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Full text of "Comets"

Glass. 
Book. 



COMETS 




By 

L. ADOLPH RICHARDS 

M. A,, M. S. 



Copyright, 1909, by L. A d o 1 p h Richards 



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Comets 



Of all the heavenly bodies with which astronomers have to 
deal, comets are among the most interesting. The appearance 
of these objects strikes most forcibly the attention of mortals, 
and their rarity, their singularity, their mysterious aspect, aston- 
ish the most indifferent minds. The phenomena which are con- 
stantly or regularly reproduced before our eyes, the things which 
we see every day may no longer excite either our attention or 
our curiosity, but in all countries and at all epochs the strange 
aspect of these mysterious visitors, traveling from out the depths 
of space, their sudden appearance and the pale gleam of their 
nebulous comas have produced on the minds of men the effect 
of a formidable powder menacing the very order established at the 
Creation. It is the unanimous testimony of history during a 
period of over 2000 years, that comets were omens of impending 
evil and messengers of an angry Deity. They were peculiarly 
"Ominous of the wrath of Heaven, and as harbingers of wars 
and famines, of the dethronement of monarchs, and the disso- 
lution of empires." 

The appearance of some of the great comets, according to 
the accounts we have of such events, form one of the most impos- 
ing of all natural phenomena. We are not, therefore, surprised 
that feelings of awe and astonishment should be excited by the 
sudden and unexpected appearance of some of these objects. 
They have always been objects of dread to the superstitious 
and to the uninstructed and an enigma to those most conversant 
with the wonders of creation and the operations of natural 
causes. 

The learned Greeks and the Romans, who with the other 
great nations have shared in this universal awe and dread, have 
handed down to us, often with circumstantial minuteness, the 



aspects of remarkable comets. To some, these bodies were ter- 
restrial exhalations, kindling in the region of fire, but to others, 
they were the spirits of great men, which were mounting to 
the sky, and which in leaving it, were handing over our poor 
planet to the plagues with which it is so often attacked. In the 
year 43 B. C, during the celebration of the games given by the 
Emperor Augustus in honor of Venus, a hairy star seen for 7 
days under the Great Bear. It was very brilliant and was seen 
in all parts of the world. The Romans appear to have seriously 
believed that this comet was really the spirit of Julius Caesar 
on its way to join the ranks of the immortal gods. Ovid, in his 
great work dedicated to Augustus Caesar, concludes with this 
same metamorphosis. He says, "Venus descends from the ethe- 
real vaults, invisible to all eyes, and stops in the midst of the 
senate. From the body of Caesar she takes his spirit, prevents 
it from evaporating, and bears it to the region of the stars. In 
rising, the goddess feels it transformed into a divine and glow- 
ing substance. She allows it to escape from her bosom. The 
spirit flies away beyond the Moon and becomes a brilliant star, 
which draws through a long space its ignited hair." 

Dion Cassius says that simultaneously with the above event 
there was seen a burning torch and an unknown star which shown 
for many days. Pingre thinks that the ''torch" was simply a 
meteor but that the "unknown star" was the same as the comet 
seen in China in May of the same year. 

Pliny describes a comet which had a "whiteness so brilliant 
that one could hardly look at it." This is the same comet which 
Josephus describes as so horrible and which showed itself during 
the terrible siege of Jerusalem. 

Halley's comet, which has become so famous and of which 
we shall speak later on, created a due amount of alarm on its 
appearance in the year 837. An anonymous chronicler of the 
time speaks of it thus: 

"In the midst of the holy days of Easter, a phenomenon 
always fatal and of sad omen, appeared in the sky. From the 
time that the Emperor, who gave much attention to such phe- 
nomena, had perceived it, he gave himself no rest. 'A change 



of reign and the death of a prince are announced by this sign' 
he said to me. Hie took counsel of the bishops and they advised 
him to pray, build churches, and found monasteries — which he 
did." He died three years later. 

The next appearance of this comet occurred in 1066, when 
William the Conqueror was about to invade England. ''Nova 
Stella, novus rex," was the proverb of the time. The chroniclers 
were unanimous in writing : "The Normans guided by a comet, 
invaded England." 

While Europe was still a prey to the emotions produced 
by the terrible news of the capture of Constantinople by the 
Turks, when the church of Saint Sophia was converted into a 
mosque and all the Christian people were either killed or reduced 
to captivity; while men were trembHng for the safety of Chris- 
tianity, Halley's comet again makes its appearance. This most 
celebrated of its appearances occurred in June, 1456. The his- 
torians of the time say "it was large and terrible, its tail cov- 
ered 60 degrees ; it had a brilliant gold color, and presented the 
aspect of a waving flame. They considered it a certain sign of 
Divine wrath. In so great a danger, Pope Callixtus HI. ordered 
that the bells in all the churches sh(5uld be rung every day at 
noon, and he invited the faithful to say a prayer in order to exor- 
cise the comet and the Turks. From this time dates the "An- 
gelus." The custom is still kept up among all Catholic nations, 
although we have no longer any fear of comets and still less of 
Turks. 

Swords of fire, bleeding crosses, flaming daggers, spears, 
dragons' mouths and other names of the same kind were lav- 
ished on comets in the Middle Ages and the Renaissance. The 
comet of 1618 A. D. inspired the following lines: 

"Eight things there be a comet brings. 
When it on high doth horrid range ; 
Wind, Famine, Plague, and Death to Kings, 
War, Earthquakes, Floods, and Direful Change." 

White, in his "History of the Doctrine of Comets," says 
these lines were to be taught in all seriousness to peasants and 

3 



school children. Milton, in his great epic poem, makes several 
allusions to comets and in so doing expresses the ideas and sen- 
timents which in his time were associated with those objects. 
In describing the hostile meeting between Satan and Death 
before the Gates of Hell, he says: 

*'On the other side, 
Incensed with indignation, Satan stood 
Unterrified, and like a comet burned. 
That fires the length of Ophiuchus huge 
In the arctic sky, and from his horrid hair 
Shakes pestilence and war." 

— II-706-11. 
Again, when the Cherubim, descends to take possession of 
the Garden, prior to the removal of Adam and Eve: 

"High in front advanced. 
The brandished sword of God before them blazed. 
Fierce as a comet; which with torrid heat. 
And vapour as the Lybian air adust 
Began to parch that temperate clime." 

— XII-632-36. 

The comet of 1528 must have struck terror to the hearts of 
the beholders. The celebrated surgeon, Ambrose Pare, one of 
the most learned men of that time, in a chapter on "Celestial 
Monsters" thus describes it: 

'This comet was so horrible, so frightful and it produced 
such great terror in the vulgar, that some died of fear and others 
fell sick. It appeared to be of excessive length and was the 
color of blood. At the summit of it was seen the figure of a 
bent arm, holding in its hand a great sword, as if about to strike. 
At the end of the point there were three stars. On both sides of 
the rays of this comet were seen a great number of axes, knives, 
blood-colored swords, among which were a great number of 
hideous human faces, with beards and bristling hair." 

The famous comet of 1680 deeply impressed all men — Jews, 
Turks, Catholics and Protestants were afraid. Even the learned 
Bernonilli himself says, in speaking of this comet, "If the body 

4 



of the comet is not a visible sign of the wrath of God, the tail 
might well be one/' 

Coming down to a more recent date, we find that as late as 
1892 considerable fright was manifest when it was supposed 
that Biela's comet was about to strike the earth. The following 
dispatch from Atlanta, Georgia, was printed in one of the daily 
papers: "The fear which took possession of many citizens has 
not yet abated. The general expectation hereabouts was that 
the comet would be heard from on Saturday night. As a result, 
the confessionals of the two Catholic churches here were 
crowded yesterday evening. As the night advanced there were 
many who insisted that they could detect a change in the atmos- 
phere. The air they said, was stifling. It was wonderful to see 
how many persons gathered from different sections of the city 
around the newspaper offices with substantially the same state- 
ment. As a consequence, many families of the better class kept 
watch all night, in order that if the worst came they might be 
awake to meet it. The orgies around the colored churches would 
be laughable, were it not for the seriousness with which the wor- 
shipers take the matter. To-night (Saturday) they are all full, 
and sermons suited to the terrible occasion are being delivered." 

So much for the fear and dread which the comets have 
caused in all times and among all peoples. We may now ask, 
what constitutes these bodies which have struck terror to so 
many hearts. Up to the time of Newton, the nature of these 
objects was entirely unknown. And we must confess that even 
at the present date we are not entirely and completely decided 
on the structure of comets. The absolutely imperceptible effect 
produced by comets upon the motions of planets or other bodies 
approached by them, show that, whatever may be the matter of 
which they consist, it must be extremely rare and feebly con- 
densed. Comets have passed nearer the Earth than a quarter 
of the distance of Venus from our planet and yet we have not 
perceived the least effect produced by them. Comets are so 
transparent that stars have been seeii shining through their cen- 
tral parts without suffering any diminution of light, nor any 
refraction manifested by the slightest alteration in the apparent 

5 



place of the observed stars. Sir John Herchel describes their 
texture, therefore, as ''almost spiritual." We must not conclude 
from this that the comet is an ''airy nothing." As we have said 
before, we have not been able to detect any action whatever 
produced by a comet on the Earth or any other body of the plan- 
etary system. Yet they have frequently come so near the Earth 
and other planets that their own orbits have been entirely trans- 
formed and, if their masses had been as much as yoirro'o'o 
of the Earth's, they would have produced very appreciable 
effects upon the motions of the planets which disturbed them. 
But a body weighing only one-millionth as much as the Earth 
would contain 6,000 millions of millions of tons. Therefore, 
we must not hastily conclude that, because the comet is so 
extremely rare and feebly condensed it possesses no material 
substance. 

We shall see further on that the tail of the comet is its 
bulkiest part but in many of the comets the head is enormous. 
The head of the great comet of 1843 was about 30,000 miles 
in diameter. The head of the comet of 181 1 was very great. 
Schroter says that the nucleus of this comet alone had a diam- 
eter of 2600 miles and that the nucleus of the 1843 comet was 
still greater. 

If the comet be a material substance to which the law of 
gravitation applies then it must move in a conic-section and 
having the Sun in one focus, the radius vector must sweep out 
equal areas in equal times. Now, Newton examined the large 
comet of 1680 and found that it acted in just this way. From this 
time on comets have been regarded as members, at least tem- 
porarily, of our solar system. 

The most reasonable theory it would seem is that ^the 
nucleus of the comet is composed of a mixture of gaseous mat- 
ter and of numerous small solid particles, dust particles or 
meteoric fragments k may be, and these, when exposed to the 
Sun's heat, throw off luminous nebulous particles that are swept 
by some repulsive force into space and form the appendage 
known as the tail. If we accept this theory, we must, however, 
remember that the particles must be very small and widely sep- 

6 



arated from each other. However, the size of the soHd bodies 
is largely a matter of conjecture. Some think they are like 
grains of sand and others liken them to paving-stones or brick- 
bats. The nucleus is supposed to be the densest portion of this 
swarm of bodies and the nuclei of some large comets may be 
small solid bodies of great density. That portions of the solid 
matter become liquid temporarily, when a comet like that of 
1882 dashes through the Sun's corona, is almost inevitable. The 
comet of 1843, which approached within 32,000 miles of the 
Sun, was exposed to a heat sufficient to volatilize the most 
infusible substances known to exist. Sir Isaac Newton calcu- 
lated the comet of his time to be two thousand times hotter than 
red-hot iron; but this calculation was made on the supposition 
that the Sun was afire and the comet as dense as the Earth. 
But neither of these suppositions is true. The Sun is not fire 
and comets, as we have shown before, are not so dense as the 
Earth. 

We see the comet only when it is in that small part of its 
orbit nearest the Sun and all this time, the Sun's heat is evap- 
orating it and probably producing chemical and electrical effects. 
Here Spectrum Analysis, which has shown its usefulness in so 
many ways, lends us its aid. Until this analysis was introduced, 
nothing was known as regards the actual composition of comets, 
except the fact that their light showed traces of polarization 
which proved that part at least of it was reflected sunlight. The 
first application of the spectroscope to the study of comets was 
made in 1864 by Donati, the discoverer of the magnificent comet 
of 1858. H]e obtained a spectrum of three bright bands which 
were wider than the ordinary lines. He was not, however, 
able to identify them. Four years later Sir William Huggins 
obtained a similar spectrum and identified it with that of a com- 
pound of carbon and hydrogen. Nearly every comet which has 
been examined since then has shown the bright bands in the spec- 
trum. This indicates the same or some other hydro-carbon, but 
in a few cases other substances have also been detected. We 
see, therefore, that a comet is, in part, at least, self-luminous, 
and some of the light which we receive from it is that of a glow- 

7 



ing gas. It also shines to a considerable extent by a reflected 
sunlight as there is nearly always a continuous spectrum, and 
in a few cases — first in 1881 — the spectrum has been distinct 
enough to show Fraunhofer lines crossing it. But the contin- 
uous spectrum seems also to be due in part to soHd or Hquid 
matter in the comet itself, which is 'hot enough to be self-lumi- 
nous. Again, those comets which have approached the Sun 
more closely than others have exhibited in their spectra, when 
near him, other lines, known to be produced by some metals 
when in a state of vapour. 

Now, as to the tails of the comets. This train of tenuous 
matter, streaming from the head is, to the naked eye, the chief 
glory of a large comet. The tail is by far the bulkiest part of 
a comet and the tail of the great comet of 1680 was found, by 
Newton, to have been, when longest, not less than 123,000,000 
miles in length. Prof. Pierce says the comet of 1843, about 
three weeks after its perihelion passage, had a tail of over 200,- 
000,000 miles in length but later determinations give its length 
as 108,000,000 miles. The comets of 1769 and 1618 also had 
very long tails. The tail of the former extended to a distance 
of 97 degrees from the head and the latter a distance of 104 
degrees. The tail of a comet is usually shaped like a bent cone 
projecting behind the comet from the Sun and at its outer ex- 
tremity is millions of miles across. 

The volume of the tail of the comet of 1882 is estimated 
to have been 8,000 times that of the Sun. The development of 
these enormous tails takes place when the comet approaches 
the Sun. 

The researches of Bessel, Norton and especially the recent 
investigations of the Russian astronomer Bredichin, have shown 
that the theory that the tail is composed of miatter repelled by 
both the comet and the Sun, not only accounts for almost all 
the details of the phenomena, but that it agrees mathematically 
with the observed position and magnitude of the tail on dif- 
ferent dates. Also, if the tail be formed by an outpouring of 
matter from the comet, which always takes place when the 
comet is near the Sun, the more often a comet approaches the 

8 



Sun the miore we should expect it to waste away. This is given 
as a reason for the short-period comets being so inconspicuous. 
By ordinary dynamical principles, matter shot off from the head 
of the comet while it is revolving round the Sun would give 
just such a curvature to the tail as it usually possesses. Like- 
wise the variations in curvature of the tails of different comets, 
and the existence of two or more different curved tails of the 
same comet, are thus readily explained by supposing them made 
of different materials, repelled from the comets head at different 
speeds. Of this Bredichin's theory gives a complete explana- 
tion. He divides tails of comets into three types: First, those 
absolutely straight in space, or nearly so, like the tail of the 
great comet of 1843 ; second, tails gently curved like the broad 
streamer of Donati's comet of 1858; third, short bushy tails 
curving sharply round from the comet's nucleus, as in Encke's 
comet. The origin of tails of the first type is related to ejections 
of hydrogen, the lightest element known, and the Sun's repul- 
sive force is in this case 14 times stronger than his gravitative 
attraction. The slightly curved tails of the second type are due 
to hydrocarbons repelled with a force somewhat in excess of 
solar gravity. In producing the sharply curved tails of the 
third type, the Sun's repellent energy is about one-fifth of his 
gravity and these tails are formed from emanations of still heav- 
ier substances, principally iron and chlorine. It is not very unus- 
ual for comets to show tails of two different types at the same 
time. The comet of 1744 is reported to have had six tails diverg- 
ing like a fan. We shall have occasion later to speak of these in 
connection with some of the well known comets. As we have 
said before, the motions of comets were not understood until 
the time of Newton, when to the comet of 1680, he applied his 
great principle of universal gravitation and showed that it moved 
in an elliptic orbit round the Sun. 

Senaca says that AppoUonius the Myndian, who was very 
skilful in Natural Sciences, affirmed that comets were by the 
Chaldeans reckoned among the planets and had their periods 
or courses like them. He says further that AppoUonius used 
to say that a comet was a star or celestial body like the Sun or 

9 



Moon; but that he did not know its course, because it ranges 
through higher parts of the world, and then at last appears 
when it comes from the bottom of its course. 

Diodorus Siculus tells us that the Chaldeans, by a long 
course of observations, were able to predict the appearance of 
comets. As we have no record of these predictions, we will have 
to accept this with much hesitation. To Senaca we must pay our 
greatest respects for his note which anticipated the explaining 
of the motions of these bodies. By an effort of philosophy supe- 
rior to the notions of his age, he did not adopt the received opin- 
ions respecting comets, but says, 'T don't think a comet to be 
a sudden fire, but one of the eternal works of Nature. A time 
will come when these things, which are now hid, will at last be 
brought to light, by length of time and the diligence of po.sterity. 
One age is not sufficient to make such great discoveries. A time 
will come when those that come after us will wonder that we 
were ignorant of things so plain," and further he says, "Some- 
body will demonstrate which ways comets wander, why they 
go so far from the rest of the celestial bodies, how big and what 
sort of bodies they are." Sixteen centuries rolled away before 
this prediction was fulfilled, but in Sir Isaac Newton all these 
predictions have been accurately fulfilled. To him is applicable 
the expression of the poet: 

"He first of men, with awful wing pursued 
The comet through the long elliptic curve, 
As round innum'rous worlds he wound his way; 
Till, to the forehead of our ev'ning sky 
Returned, the blazing wonder glares anew 
And o'er the trembling nations shakes dismay." 

The comiet of 1680, was first seen with a telescope by Got- 
fried Kirch, at Corbury in November. It is sometimes called 
Newton's comet because, as we have stated before, in reference 
to it he showed the applicability of the law of gravitation, and 
should it appear in 2255, it will probably be regarded as a me- 
morial of Newton. Upon the principle of the law of universal 
gravitation, Newton calculated its orbit and found that the 

10 



comet was moving in a long elliptic orbit, requiring several 
centuries to traverse. Newton as well as Halley thought that 
it might be identical with large comets seen in A. D. 1106, 
A. D. 531, and B. C. 44, the one which appeared just after the 
death of Julius Caesar. More recent calculations, however, 
show that the period of the comet of 1680 is more than the 
interval 575 years, but it is impossible to determine this accur- 
ately from observations made at the one appearance. We have 
no exact observations of the comets of 43 B. C, 531 A. D. and 
1 106 A. D. We cannot calculate their orbits and therefore we 
lack the only criterion by which we could decide with certainty 
the identity of these comets. We do know that those of 1680 
A. D., of 1 106 A. D., of 531 A. D., and of 43 B. C. were very 
brilliant and we find that the time elapsing between these ap- 
pearances is roughly 575 years. 

From 1 106 to 1680 we have 574 years. From 531 to 1106, 
we have 575 years. From 43 to 531 is 575 years. 

The next remarkable comet was the famous Halley's comet, 
which appeared in 1682. This appearance led to the first suc- 
cessful prediction of a return of a comet. It was made by Dr. 
Halley, the contemporary of Newton. Hialley's prediction was 
fulfilled (16 years after his death) by the comet's reappearance 
in 1758. Halley calculated the elements of the orbit of the comet 
of 1682 and applied the same methods of calculation to the 
observations which Kepler had made on the comet of 1607. He 
found that this gave results in regard to the inclination of its 
orbit, the place of its node, the situation of its. perihelion, and 
the retrograde direction of its movements, so closely comparable 
to the first set that there 'was little doubt that it was the same 
object. Between these two periods there was an interval of 
75 years. In reckoning backwards from 1607, he found that in 
1 53 1 or 1532 a similar comet had been observed and the results 
deduced were almost precisely the same. Going still further back, 
he found that a similar comet had appeared in 1456. 

This was the comet which excited such great consternation 
in Europe, its appearance having been regarded as connected 
with the menacing success of the Mahomedan armies. Since 

II 



there were not sufficient observations on this comet its elements 
could not be determined. Also a remarkable comet recorded as 
having been observed in 1305 or two 75 year periods previ- 
ously, and also one in 1230 were reasonably supposed to have 
been the same. 

Having shown these identities, Halley confidently predicted 
that the comet would reappear in 1758 or the beginning of 1759. 
He reaHzed that there was some influence at work which was 
causing some slight change in the comet's period and hence he 
left the precise time of return in some degree of uncertainty. 
However, he was confident in his prediction and desired that 
it should be remembered that its author was an Englishman. 

In Halley's time, it was impossible to determine with exact- 
ness the values of these perturbations — the difficult problem 
which Clairant has resolved. Clairant found that by reason 
of the diminution which the attraction of the planets causes in 
its progress, the comet would employ 618 days more to return 
to the perihelion than in the preceding revolution. This was 100 
days from the effects of Saturn and 518 days by the action of 
Jupiter. The passage then, should correspond with the middle 
of April, 1759. Clairant reserved 30 days of grace, for he said 
he had neglected small values in his calculations. All these 
predictions were fully justified, for according to expectation, the 
comet passed its perihelion on the 12th of March, 1759, within 
the assigned limitation. Halley's comet returned again in 1835 
and we may expect it again in 1910. 

There are many other comets which are remarkable because 
of some striking peculiarities or because of circumstances con- 
nected with their discoveries. Of these we can here mention 
only a few. We have seen that the period of revolution of a 
comet is usually large and in some cases it is enormous. It 
is therefore interesting to note that Encke's comet has the honor 
of being our most frequent visitor, having the shortest known 
time of revolution. Its period is only three years and a half. 
This comet has been observed at almost every return since 18 19, 
the year in which Encke detected its periodicity. It had been 
observed frequently during the 50 years preceding this date. 

12 ' '^: 



This comet shows a very conspicuous change in diameter as it 
approaches and recedes from the Sun. When it is at perihe- 
lion its volume is only about t-o,V"oo of what it is when first 
seen. This comet is also remarkable in that, since its discovery 
in 1819, it has been continually quickening its speed and short- 
ening its period at the rate of about two hours and a half in 
each revolution; as if it were under the action of some resisting 
medium. 

We have before referred to the scare produced by the comet 
of 1832 when it approached so near the Earth and gave rise to 
the first comet scare of the century. It was discovered in 1826 
by an Austrian, named Biela. It was the second of the short- 
period comets in order of discovery. Its period was 6.6 years. 
We are very much concerned about this comet because after 
acting very strangely on two of its returns, it became "lost" and 
we have never .seen it since, although it should have paid us 
five other visits. 

On its return in 1846 it showed that it had met with some 
mishap for it was now divided into two and when last seen the 
two parts were traveling quietly in their appointed orbit but sep- 
arated by about 1,500,000 miles. Miss Gierke says, 'Tt became 
evident that Biela's comjet was shedding over us the pulverized 
products of its disintegration," when on the night of November 
2"], 1872, just as the Earth was passing the old track of the 
lost comet, she encountered a wonderful meteoric shower. Miss 
Gierke's view may be correct but it is perhaps expressed a little 
too positively. 

Donati's comet of 1858 must be mentioned, for, although 
not the largest or most extraordinary, it was on the whole the 
finest comet of the century. The exhibition of the unrivaled 
perfection of the development and structure of concentric en- 
velopes have made it the normal and typical comet. Its tail was 
of the second or hydro-carbon type with faint tangential stream- 
ers which belong to the first or hydrogen type. Its periodic 
time is nearly 2,000 years. 

The great comet of 1882, which we have referred to before, 
will always be remembered not only for its beauty but for the 

13 



great variety of unusual phenomena which it presented. It 
was first seen with the naked eye at Aukland, New Zealand, on 
September 2, and by the 8th, it had been observed at Cordova, 
(South America) and at Cape of Good Hope. It was so bright 
that by merely shutting off the Sun with the hand, there was not 
the slightest difficulty in seeing it. 

Swift's comet of 1892, is remarkable on account of the mar- 
vellous changes observed in its tail. On April 4th, it was 20° 
long, straight and slender. The next morning a new tail had 
formed between the other two, and each tail was composed of 
several lying close together. At least a dozen could be counted. 
After the lapse of another day, one of the original three tails 
had vanished, and the other two were blended. Then one of 
these grew bright and the other faded away; the bright one 
had a sharp bend in it, as if turned aside by some obstacle. 
Finally, the tail split up into six branches. All these changes 
and some others took place within five days. 

We must not pass over Dr. Brooks' comet. Dr. Brooks is 
known in astronomical circles as the comet finder. (Smith and 
Barnard also share this honor.) On the 24th of the present 
month (May 24, 1909) he has just discovered at the Smith 
Observatory, Geneva, N. Y., an object which he thus describes: 
"The object was visible in the eastern sky from 2 to 3 o'clock 
this morning. It had the appearance of a gigantic 'naked-eye' 
comet, with a large head and a tail of enormous proportions. 
When first seen the head was in the great square of Pegasus 
and the tail stretched upward toward the north star, at one time 
reaching the chair of Cassiopeia. The motion was rapidly east- 
ward. At 2.30 a. m. the head enveloped the star Algenib, and 
by 3 o'clock it had reached the horizon. Soon afterward the 
tail was lost in the rapidly advancing dawn." This is the twenty- 
sixth comet discovered by him, fifteen of these having been dis- 
covered at the Smith Observatory during the last sixteen years. 
The other eleven were discovered at the Redhouse Observa- 
tory, Phelps, N. Y. The comet which bears Brook's name is 
the one discovered on the morning of October 17, 1892. A pho- 
tograph taken by Dr. E. E. Barnard on the morning of October 

14 



21, showed remarkable changes in the tail which Dr. Barnard 
thus describes: 

"It presented the comet's tail as no comet's tail was ever 
seen before: The graceful symmetry was destroyed: the tail 
was shattered. It was bent, distorted, and deflected, while the 
larger part of it was broken up into knots and masses of neb- 
ulosity, the whole appearance giving the idea of a torch flicker- 
ing and streaming irregularly in the wind. The short northern 
tail was swept entirely away, and the comet itself was much 
brighter. The very appearance at once suggested an explana- 
tion which is probably the true one. If the comet's tail, in its 
flight through space, had suddenly encountered a resisting me- 
dium which had passed through the tail near the middle, we 
should have precisely the appearance presented by the comet. 
It is not necessary that the medium should be a solid body; if 
it possessed only the feeblest of ethereal lightness it would 
deflect, distort and shatter the tail. What makes this explana- 
tion all the more probable is that the disturbance was produced 
from the side of the tail that was advancing through space." 

Within less than a month after the discovery of the comet 
mentioned above, Mr. Holmes, an English amateur astronomer, 
on November 6, 1892, discovered a comet which has his name. 
This comet was supposed, by some, to be the lost Biela's comet, 
since it occupied about the same position in the sky as Biela's 
should occupy, if still in existence, and the latter was due at this 
time. It is peculiar in that its orbit is more nearly circular than 
that of any other known comet. Its period is less than seven 
years. 

The little comet which was seen in Egypt on May i6th, 
1882, was distant from the Sun about the amount of the Sun's 
diameter. It was seen with the naked eye during the eclipse of 
the Sun. It was of course seen for a few moments only and it 
has never again been seen. It is chiefly interesting in that its 
existence was recorded on several of Dr. Lockyer's photograph 
plates while he was photographing the eclipse. During the 
total eclipse which occurred on April 16, 1893, another comet 
was photographed in the corona. This comet was very much 

15 



fainter and more difficult to recognize than the one photo- 
graphed in 1882. Some think the two comets may be identical, 
with a period of about 11 years. 

We have here spoken of only those comets which from their 
associations, their size, or other distinguishing characteristics, 
have been rendered somewhat more remiarkable than their 
numerous associates. In this limited space it would be impos- 
sible to give accounts of all the comets which have been care- 
fully observed and their orbits and periods determined. Includ- 
mg the returns of the periodic comets, there are now on the lists 
about 700. There is seldom a day when at least one comet is 
not in sight and to this number are added as higjh as 4 or 5 
each year. 

We have found that neither fear nor dread need be appre- 
hended from their visits. 'They come to please and instruct, 
not to injure or destroy." There are authentic astronomical 
records which relate to a point of time four thousand years 
back and ancient zodiacs, hieroglyphics and astronomical fables, 
referring to a yet more remote period. Still we have no account 
of comets ever doing any mischief. They have become our best 
teachers in that they never fail to hold our attention and to 
awaken in us the desire to know more about the lessons we may 
derive from them. They are welcome visitors and we hail with 
delight not only their first visit but also the return of the peri- 
odic comets. 



Note : The astronomers of the world are preparing to welcome 
back from the regions of space, a comet which for more than seventy 
years has been out of mortal sight. For thirty-eight years it traveled 
away from the Sun at the rate of more miles a minute than the fastest 
railroad train can make in a whole day and went so far that it was a 
half million miles beyond Neptune, and Neptune is at the edge of our 
solar system, more than 3,000,000,000 miles away from the Sun. For 
more than thirty years this heavenly traveler has been coming towards 
us at this same tremendous speed — 26 miles per second. By the middle 
of May, 1910, it will have approached to within 95,000,000 miles of us. 
Then it will turn back once more, and speed away on its 76 years 
journey through space. 

This strange visitor is none other than the famous Halley's comet 
to which we have alluded several times before in this brief treatise. 



16 




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